Gulp! (Er, rather, don’t if you’re pregnant.) A new study published online this week in the journal Alcoholism: Clinical and Experimental Research has found that a fetus can be harmed by drinking during any point in pregnancy—but especially at the end of the first trimester, reports TIME.com. The authors say the study is one of the first to examine the impact of alcohol exposure (including quantity, frequency and timing) on a spectrum of abnormalities known as fetal alcohol syndrome.

Between 1978 and 2005, scientists at the University of California, San Diego gathered confidential, specific information from 992 women about their consumption of alcohol and other substances every three months during their pregnancies, including dates of use, drinks per day, number of binge episodes and maximum number of drinks. This study is unique in that the information was gathered during the pregnancies—and thus before any effects on the fetus could be known. Following the births, the newborns were examined by a dysmorphologist (a specialist in structural birth defects) to look for evidence of fetal alcohol syndrome and other conditions.

Every one additional drink the women consumed between their 43rd and 84th days of pregnancy (the second half of the first trimester) resulted in a 25 percent greater chance of having a smooth ridge between the nose and upper lip, a 22 percent greater chance of having an abnormally think lip, a 12 percent greater chance of having a smaller-than-normal head, a 16 percent greater chance of reduced birth weight (which could put the babies at greater risk for physical and mental problems) and an 18 percent greater chance of reduced birth length.

The study authors write, “Based on our findings, there is no safe threshold for alcohol consumption during pregnancy with respect to selected alcohol-related physical features. Women who are of childbearing age and who are contemplating or at risk of becoming pregnant should be encouraged to avoid drinking, and women who are pregnant should abstain from alcohol throughout pregnancy.”

Did you ever drink during pregnancy? Would this study make you abstain completely?